The present invention relates to a polishing apparatus and a method of polishing a work piece, e.g., silicon wafer.
In conventional polishing apparatuses for polishing work pieces, e.g., silicon wafers, atmospheric conditions of the apparatuses or their polishing sections, e.g., pressure, temperature, humidity, are not specially controlled. Therefore, especially in chemical-mechanical polishing apparatuses, stable machining characteristics cannot be gained. To solve the problem, the inventors of the present invention have invented a pressure vessel type polishing apparatus, which has a pressure vessel whose atmosphere can be controlled (see Japanese Patent Gazette No. 2003-225859). The polishing apparatus is capable of improving polishing efficiency.
In case of chemical-mechanical polishing, a pH value of slurry greatly influences polishing rate and quality of products. In a conventional open-type polishing apparatus, a pH value of slurry delicately changes according to the atmospheric conditions. Therefore, it is difficult to precisely control the pH value of the slurry.
Further, in the case of chemical-mechanical polishing, it usually takes 2–7 minutes to gain normal machining characteristics after dressing a polishing pad. After dressing the polishing pad, a surface of the polishing pad is cleaned by pure water, so it takes a long time to completely remove used slurry therefrom. Especially, in case of changing to different type slurry during the chemical-mechanical polishing process, it takes 10 minutes or more to completely exchange slurry.
Especially, in the pressure vessel type polishing apparatus, polishing conditions must be rapidly changed without exchanging slurry.